Chandragupta Maurya and Chanakya with help of Parvatak and after great efforts had successfully captured Patliputra.
After Dhan Nanda pleaded mercy to Chanakya, he allowed him to leave with his important things for his sustenance which his one chariot could hold.
Nanda took his two wives, a daughter and loading his chariot with treasures he left the city.
When the family met Chandragupta Maurya on the road, the daughter of Nanda sitting in the chariot fell instantly in love with Chandragupta at first sight (probably due to his handsome appearance). With her side glances, it looked like she was infatuated with him.
Nanda allowed her to choose her own husband as Swayamvar was considered befitting of a princess.
She left her father's chariot and ran towards Chandragupta’s chariot. When she put her foot on his chariot, nine spokes of a wheel broke.
Angry Chandragupta shouted “Who is this inauspicious woman trying to climb my chariot?” He forbade her to climb his chariot.
But Chanakya told him to stop her and not think the accident as a bad omen but an auspicious one. It meant his dynasty would run for nine generations.
So, after Chanakya told him this, he (half heartedly) accepted the Nanda Princess.
Source - Parishisth Parvan
The story seems a little dramatic and it might be possible that after the conquest of Magadha, Chanakya advised him to marry a daughter of Nanda. The daughter unable to change her fate and founding the new King good looking didn't have much problem in accepting the new reality but Chandragupta had his doubts. But ultimately Chanakya convinced him to marry her for the good of his dynasty.
The Princess is mentioned as ‘Nand Nandini and ‘Nand Duhita’ and this might be the reason for this Nandini name but it wasn't a name, both terms means daughter of Nanda. The name of daughter of Nanda is not mentioned by Hemachandra, author of Parishisth Parvan.
The aftermath of their marriage is not mentioned in the source, there is no mention of his conflict with anyone of his queens. So, it might had been a tolerable marriage for the couple if not a very loving one.
